It is often desirable to impart visual effects such as three dimensionality or motion characteristics upon articles of consumable products and the like. Dimensional image display devices or sheets are used to create these desirable visual effects such as, for example, 3D effects, magnification, animation, depth, morphing, flipping, hidden codes or messages, and other such types of graphics. The dimensional image display sheets can be applied to or used as various articles as eye-catching promotional tools, advertising, branding, games, and the like. Examples of articles can include, for example, sports cards, game cards, containers, cups, cup inserts, wraps, and sleeves, packaging materials such as packaging boxes, wrappers, tubes such as toothpaste tubes, envelopes, greeting cards, invitations, napkins, posters, business cards, fabrics and clothing, billboards, stickers, labels, badges, pens, magnets, postcards, identification or stored value cards, such as gift cards, credit cards, rewards cards, wall paper, folders such as pocket folders, media packaging such as DVD or CD covers, and any of a variety of articles.
Dimensional image display devices typically incorporate a printed image proximate a lens sheet having a lens array thereon. The printed image can be either directly bonded or printed to the lens array, or printed on a separate substrate and laminated to the lens array. Image segments or elements are printed using high resolution, and precise registration techniques to form the overall image. One such printing technique includes interlacing images, in which a composite of two or more images are interlaced with each other in individual slices or segments to form the overall image that will be viewed through a lens array. The interlaced image is then configured or mapped so that each lens of the array focuses on at least a portion of the interlaced image. The interlaced image is configured to accommodate both viewing distance and curvature through the lens.
One type of dimensional imaging technology well-known in the art includes lenticular image technology. Lenticular image technology includes a lenticular image, such as an interlaced image, in combination with a lenticular lens array. The lenticular lens array is formed from a web or sheet including a plurality of substantially parallel elongated cylindrical lenticules or lenses extending from one surface. The second surface is planar. Typically, the lenticular lens array is formed from a plastic material and can be formed from any of a variety of techniques including casting, coating, embossing, extruding, and the like. The interlaced image can be printed directly on the planar second surface, or can be printed on a separate substrate and subsequently laminated to the lenticular lens array by a clear adhesive, fusing, compression lamination, or other similar techniques. Examples of lenticular image technology can be found in U.S. Pat. No. 6,900,944 to Tomczyk; U.S. Pat. No. 6,424,467 to Goggins; and U.S. Pat. No. 7,359,120 to Raymond et al., the disclosures of which are incorporated herein by reference.
Currently available methods can provide a lens sheet or lenticulated sheet array, which can vary in thickness or caliper, for example, from about 10 mils to about 40 mils. The thickness of the extruded lenticular lens layer is suggested by the formula: r=C×f or r=[(n′−n)/n′]×f where r is the radius of curvature of a lenticular lens, C is a constant, f is the focal length of optimal focus thickness for the plastic, n′ is the index of refraction of the lens construction material, such as an extruded plastic, and n is index of refraction of air. From the formula it is evident that the thicker the plastic, the lower the pitch or lenticules per inch (LPI), and the lower the pitch, the coarser the lens. A coarse lens can give undesirable lens effects, for example, distortion of an underlying image. A coarser lens requires image graphics and text to be significantly large to avoid undesirable lens effects. When printing a lenticular image on a lenticular lens, the lens needs to be parallel to the interlaced image, such as, for example within +/−½ lenticule per ten inches. If this is not maintained, the image does not have an acceptable vertical flip, but rather a skewed flip. Skew can be defined as unacceptable ink-to-lens registration accuracy of the printed vertical lenticular image elements to the vertical lenticular lenses.
Another type of dimensional imaging technology includes fly's eye or bug's eye image technology. Fly's eye or “integral” lens arrays are formed from a web or sheet including a plurality of domes or semi-circular structures extending from the surface, rather than the elongated lenses of lenticular technology. Similar to lenticular, an image, such as an interlaced image, can be printed on the planar side of the lens sheet or web, or printed on a separate substrate and laminated thereto. There are a number of benefits to using a fly's eye lens as opposed to a lenticular lens. The fly's eye lens is essentially a lenticular lens in multiple directions tangentially around the lens. This essentially allows one not only to interlace an image from left to right (horizontal direction), but also up and down (vertical direction), diagonally, or in any combination to give additional animated effects.
Current methods of producing dimensional images, such as lenticular images, include printing of lenticular sheets through a sheet-fed or web-fed press where, as discussed above, the caliper ranges from about 10 mils to about 40 mils. Alternatively, the caliper of the lens sheets or webs can be from 10 mils or less, thereby forming thin film display devices. Examples of thin film technologies are described in U.S. Pat. No. 6,424,467 to Goggins, U.S. Pat. No. 7,359,120 to Raymond et al., and U.S. Patent Application Publication No. 2010/0134895, entitled “Thin Film High Definition Dimensional Image Display Device and Methods of Making Same,” all of which are incorporated herein by reference in their entireties. Novel imaging or printing techniques, known commercially as Infinidepth®, do not require the critical ink-to-ink registration of traditional interlacing and therefore can be used on thinner lenses with higher lens densities, as described in one or more of U.S. Patent Application Publication Nos. U.S. Application Publication Nos. 2008/0088126 entitled “Layered Image Display Applications and Methods,” 2008/0088931 entitled “Layered Image Display Sheet,” and 2008/0213528 entitled “Customized Printing with Depth Effect” all of which are incorporated herein by reference in their entireties.
Whether in thin film format or thicker rigid format, it can be desirable to impart visual effects such as three dimensionality or motion characteristics on only select areas of a surface or article, as opposed to an entire surface, typically referred to as “spot” lenticular. One such method of spot lenticular is described in U.S. Pat. No. 7,002,748 to Conley et al. Another technique includes a varied lenticular lens array, in which the density and/or shape of the lenticules are altered on a single surface is described in U.S. Pat. No. 7,609,450 to Niemuth.
However, in each of these examples, the lenses extend above the base or planar surface making it difficult to print either a first surface around the lenticular features, or the second opposite planar surface after the array has been formed because the varying caliper and uneven surface makes it difficult or impossible to maintain constant pressure through a contact-based printing press, such as in offset printing, resulting in poor print quality and/or distorted lenses. For example, when a web or sheet of varying caliper is printed via an offset flexographic or lithographic printing process, the variance in caliper between the planar and lenticulated areas causes uneven pressure in the nip formed by the impression cylinder and the blanket or offset cylinder, thereby resulting in variations in color densities. A variance as little as two or more mil can result in poor quality printing. If the pressure is increased to maintain even pressure over the sheet, the lenses or lenticules are forced at high pressure either into the blanket cylinder or the impression cylinder, depending on what surface is being printed, which can result in distortion of the lenses and permanent damage to the blanket.
Further, if a lens sheet having a lens array in which the lenses extend above the planar surface is married or bonded to a substrate, such as a printed substrate, the uneven caliper or surface can cause difficulty in a nipping process (nip pressure or bonding pressure) used to mount the sheets together. Similar to the problems associated with contact-based printing, the lenses or lenticules are forced at high pressure into nip rollers, which can result in distortion of the individual lenses or caliper variation or bubbling.
When printing a number of sheets, it is common to use equipment that automatically feeds each sheet into the printing press from a stack. In both contact and contactless printing such as inkjet and other digital printing techniques, a variance in caliper of the sheet can result in poor or inconsistent autofeeding capabilities because the equipment may misjudge the location of the next sheet from the stack, either grabbing no sheet or more than one sheet due to pile curl or waviness. Similar to sheet-fed processes, caliper variance in web rolls (sometimes called gauge banding) can cause inconsistent web gauging which in turn can cause problems with unwind and/or rewind processes, as well as calibration of one or more systems in the webline, such as the uneven printing pressure described above. Furthermore, caliper variance can cause similar issues, whether in sheet or web form, in cutting processes, and/or stacking off-press. For example, in a contact-based cutting process, such as a guillotine or die-cutting process, caliper variance can cause misjudgment of the depth of cut needed, resulting in too shallow of a cut such that the web or sheet is not completely cut through, or the cut is too deep which can cause damage to the die, or even result in the die rule being buried in a cutting surface. In addition, caliper variations in the diecutter could cause infeed and stripping operation problems.
Therefore, there remains a need for a lens sheet having one or more lens arrays in select areas that can be economically and efficiently produced and printed for use with any of a variety of articles for offering special visual effects such as three-dimensionality, magnification, and/or animation, and that can be delivered in a flat format, such as a flat stack or roll.